1. Technical Field of the Invention
The present invention relates in general to a presence-based interactive communications system, and in particular, to automating the subscription/unsubscription procedure of a watcher to monitor the presence of a presentity.
2. Description of Related Art
Presence-based interactive communication services are callee-centric, where callees (presentities) publish, in real time, their presence information (such as, the availability, activity, local time, location, current status of the active devices/applications and the corresponding preferences, etc.) to callers (presence watchers). The presence information is designed to enable the callers to more efficiently and effectively contact the callees. Existing presence-enabled applications utilize a presence subscription procedure that involves the direct interaction of users (i.e., the watcher and the presentity) through their respective clients/presence user agents via the corresponding proxy presence servers. Thus, presence services currently require asynchronous, on-line input of small pieces of data by both the presentity and the watcher.
The lack of automatic mechanisms for subscribing and unsubscribing to presence services imposes restrictions on the scope of available presence-enabled services. Since current presence services only provide real-time presence information of presentities to watchers, a watcher is not able to ascertain future presence information of a presentity unless the watcher subscribes to the presence service at a future point in time. This time-constraint on presence information may be undesirable in some applications.
For example, if a watcher is interested in knowing when a change in presence status of a presentity occurs, the watcher must either remain subscribed to the presence service indefinitely or predict when the change will occur. However, for the majority of applications, a watcher is not able to accurately predict a particular future point in time during which the presentites' presence information will indicate a desired presence status. As a result, the only option available to most watchers is to remain subscribed to the presence service, which leads to unnecessary network and other resources wastage.
Therefore, what is needed is a presence system and method for resolving the unpredictability property of future events. In addition, what is needed is an event-based presence subscription mechanism that achieves a significant reduction of network traffic and cost of presence services.